Camshaft adjusters are used in internal combustion engines to vary the control times of the combustion chamber valves, in order to make it possible to variably configure the phase relation between the crankshaft and the camshaft in a defined angular range, between a maximum early position and a maximum late position. The matching of the control times to the current load reduces consumption and reduces emissions. For this purpose, camshaft adjusters are integrated into a drivetrain via which a torque is transmitted from the crankshaft to the camshaft. This drivetrain can for example be realized as a belt drive, a chain drive, or a gear drive.
In a hydraulic camshaft adjuster, the output element and the drive element form one or more pairs of pressure chambers that act opposite to one another, and to which oil pressure can be applied. The drive element and the output element are configured coaxially. Through the filling and emptying of individual pressure chambers, a relative movement is produced between the drive element and the output element. The spring, acting rotationally between the drive element and the output element, impels the drive element in an advantageous direction relative to the output element. This advantageous direction may be in the same sense as, or in the opposite sense to, the direction of rotation.
A commonly used design of hydraulic camshaft adjuster is the vane-cell adjuster. Vane-cell adjusters have a stator, a rotor, and a drive element. The rotor is usually connected in rotationally fixed fashion to the camshaft, and forms the output element. The stator and the drive element are also connected in rotationally fixed fashion to one another, and are also fashioned in one piece if warranted. Here, the rotor is configured coaxially to the stator and inside the stator. With their radially extending vanes, the rotor and stator define oil chambers (vane cells) that act opposite one another and on which oil pressure can act, and which enable a relative movement between the stator and the rotor. In addition, the vane-cell adjusters have various sealing covers. The stator, the drive element, and the sealing cover are secured by a plurality of screwed connections.
Another known type of hydraulic camshaft adjuster is the axial piston adjuster. Here, oil pressure axially displaces a displacement element that, via helical gearings, produces a relative rotation between a drive element and an output element.
A further design of a camshaft adjuster is the electromechanical camshaft adjuster, which has a three-shaft transmission (for example a planetary transmission). Here, one of the shafts forms the drive element and a second shaft forms the output element. Via the third shaft, rotational energy can be supplied to the system or carried away from the system by an actuating device such as an electric motor or a brake. Here, a spring can likewise be situated in such a way that the drive element and the output element support one another or guide one another back during their relative rotation.
DE 10 2007 039 282 A1 provides a camshaft adjuster having a cover hood that is fixedly connected to the belt pulley by snap hooks integrally formed on the cover hood. For this purpose, the belt pulley has a plurality of openings through which the snap hooks are inserted and lock. Through the use of insert elements, the snap connection is secured against later accidental detachment of the connection.